Auto is silly. I expect the better players try to even themselves out. Ie, it doesn't make sense to have ZD, Nuggz, NorgmaN, M2, etc. all on the same team; and if you wanted to stack, its easy to wait and see which side you'd be on before you auto. Further, when you join, and say the teams are like:
T: 10 ppl, score 4
CT: 12 ppl, score 1
Auto will put you on T, and possibly increase the stack. Pressing Tab might make you decide you should stack CT some more; but maybe the problem has already been fixed and you'd be overstacking CT. I usually watch the current game a bit and then pick a side accordingly. Unless I decide not to play, in which case I auto and F10 since spectate isn't always an available option. If the map is new I usually pick the hard side.